Normal powder detergents are a mixture of surfactants and inorganic builders in a ratio of about 1:1 to 1:2. When these components are concentrated into a liquid detergent form, there is a multiphase separation, particularly when nonionic surfactants are present since nonionic surfactants are not very tolerant of ionic inorganic builders.
Historically, liquid detergents have recognized and struggled with this incompatibility. In the past, manufacturers formulated built liquid detergents that separated into two phases and simply instructed the consumer to shake the product well before using it. Currently, consumers are less likely to accept liquid detergent products which require shaking before use even though such products have good cleaning performance when properly shaken to combine the separate phases together. The result has been that current commercial liquid laundry detergents are almost all surfactants with very little or no inorganic builders present. The inorganic builders are desirable because they are the lowest cost cleaning components in detergents.
Recent developments have partially solved this problem by using more expensive organic, polycarboxylate builders and by suspending inorganic builders in the liquid detergent system. Whereas these systems have been successful as a detergent, they have not provided good prespotter properties. One problem with the addition of a polymer to an aqueous liquid detergent composition, particularly to a built liquid detergent composition, is that the polymer sometimes tends to undesirably render the composition unstable and to cause phase separation.
Good detergency and good prespotting properties have also historically been incompatible in a single liquid. The best cleaning detergents have been highly built, high alkaline systems. However, in a liquid detergent, high alkalinity will fix certain stains such as coffee, tea and red wine. Highly alkaline liquids can also cause skin irritations.
This invention discloses a clear homogeneous built liquid system containing nonionic surfactants which is neutral to slightly alkaline and excellent for prespotter use.
European Patent Application EP 0 000 224 A1 to Smith et al. teaches liquid and solid detergents for improved greasy soil removal. The improved greasy soil removal properties are the result of the presence of an essential ingredient which is a 3-component active system comprising anionic surfactants, alkoxylated nonionic surfactants and water soluble cationic surfactants. It is a further example of the use of conventional hydrotrope agents in liquid detergent formulations since it teaches that conventional hydrotropes such as sodium benzoate or sodium salts of toluene, xylene or cumene sulphonates can be included for insuring phase stability of the liquid compositions. Smith et al. teach the use of water soluble polycarboxylates as detergency builders.
Furthermore, Smith et al. teach that 0.1% to about 3% of a further optional, but preferred, component can be included which is a polymeric material of molecular weight 2,000 to 2,000,000. They do not suggest using such materials as hydrotropes for built liquid detergent compositions of the type used in the present invention. That polymeric material includes a wide variety of possible polymers made by the polymerization of maleic acid or maleic anhydride with a polymerizable comonomer which includes alkyl esters of acrylic and methacrylic acid, styrene, N-vinyl pyrrolidone or monoolefins of the formula (iii) H(R.sub.4)C.dbd.C(R.sub.5)H where each of R.sub.4 and R.sub.5 is H or an alkyl group such that R.sub.4 and R.sub.5 together have 0 to 10 carbon atoms. Examples 7 and 8 of Smith et al. teach the use of GANTREZ AN119 which is a maleic anhydride/methyl vinylether copolymer. We have found that maleic anhydride/methyl vinylether copolymers do not act as hydrotropes in the present invention nor do copolymers of maleic anhydride and 1-butene. On page 30, lines 22-35 of Smith et al., the applicants teach that in place of GANTREZ AN119 in the working examples, various other maleic anhydride copolymers can be used such as an ethylene-maleic acid copolymer of molecular weight ("MW") 4,000, a propylene-maleic acid copolymer of MW 30,000, a 1-hexene-maleic acid copolymer of MW 25,000 or MW 30,000, a vinyl pyrrolidone-maleic acid copolymer of MW 26,000, among others. We have found that although 1-hexene/maleic anhydride copolymers are useful as hydrotropes in the present invention, that those copolymers containing alpha olefins with less than 6 carbon atoms as well as those made with methyl vinylether are not useful as hydrotropes. The built liquid detergent compositions of Smith et al. did not give clear, stable and single phase compositions. Thus Smith et al. does not suggest the method of the present invention and in fact specifically teaches that conventional hydrotropes should be used for insuring phase stability.
British Patent Specification No. 1 596 756 is assigned to Procter & Gamble Limited, a subsidiary of Procter & Gamble Company to which the Smith et al. patent application is assigned. The disclosure of the '756 Patent is similar to and contains a broader teaching of maleic anhydride/acid copolymers than does the Smith et al. Patent. The '756 Patent teaches solid and liquid detergent compositions which require three components: an organic detergent, a phosphate builder based on orthophosphate, pyrophosphate and tripolyphosphate salts; and a builder auxiliary which is a mixture of (i) up to 4% of a polyphosphonic acid or salt thereof and (ii) up to 4% of a homo- or copolymeric polycarboxylic acid or salt thereof. The critical features of the ingredients used are described on page 1, lines 6-29 and on page 2, lines 44-51: small amounts of a mixture of polyacids improve the performance in whiteness retention (i.e., the antiredeposition properties) and ash deposition (i.e., precipitation of insoluble phosphate salts on clothing) of detergents containing the phosphate builders noted above.
Thus, the '756 Patent requires phosphate builders which have fallen into environmental disfavor for use in detergents as well as two builder auxiliaries, one of which can be a copolymer of maleic anhydride with other polymerizable monomers. Examples 24-26 of the '756 Patent employ 1%, 1%, and 0.5%, respectively, of GANTREZ AN139 which is a copolymer of maleic anhydride and methyl vinylether. Among the variety of monomers which are taught are those of the formula R.sub.4 R.sub.6 C.dbd.CR.sub.5 R.sub.7 where each of R.sub.4 to R.sub.7 is --H or and alkyl group such that R.sub.4 to R.sub.7 together have from 1 to 20 carbon atoms, R.sub.4 to R.sub.7 each optionally being hydroxy substituted. However these polymers are used in conjunction with a polyphosphonate for a purpose different from that of the method of the present invention. A further point of difference is that on page 10, the '756 Patent teaches that when the olefins of the previously described formula are used, the copolymers are preferably of high molecular weight and are preferably based on ethylene which is not operative in the method of the present invention. This teaching is present although page 16 of the '756 Patent contains the same language concerning substitution of other maleic acid copolymers such as those employing 1-hexene as is found on page 30 of Smith et al.
Therefore neither Smith et al. nor the '756 Patent suggest the method of the present invention which requires certain specific hydrolyzed polymers of maleic anhydride and alpha olefins to serve as hydrotropes in certain built liquid detergent compositions which contain nonionic surfactants.
Detergent compositions containing polymers as builders are old and well known in the art. A number of these patents can be seen by reviewing the literature.
Erdy et al., in U.S. Pat. No. 3,691,107, disclose a novel detergent composition comprising a mixture of one or more surfactants with a unique builder which comprises a cross-linked, water-insoluble polymer of at least one C.sub.4 -C.sub.10 olefin and at least one polycarboxyl vinyl monomer. The cross-linked water insoluble polymer is a water-swellable gel forming material. This patent is of particular interest to the present art in examining Example 1, Table 1 as contained in column 11, lines 7-35. Specifically, alpha olefin maleic anhydride polymers disclosed, some of which are contemplated for use in the present invention, are disclosed as old and well known in the art. However, a reading of the Example indicates that they are being used in the Erdy patent Example as part of a powder detergent composition. No hydrotrope properties are described as being inherent in the alpha olefins of the Erdy composition and they further differ from the hydrotropes used in the present invention in that they are cross-linked with diamines and triamines and with diols and triols. The Erdy polymers are then hydrolyzed to make water insoluble swellable gels. All the examples are for powdered detergents and although they do mention an aqueous dispersion of the detergent composition, they are cloudy, two-phased liquids which do not possess the cleaning and anti-redeposition properties of the present invention. Moreover, the levels at which the alpha olefin maleic anhydride polymers are used at are a level of 40% by weight of the composition. It would appear that the use of the polymer is as a builder substitute, which is known in the art, and not as a hydrotrope or anti-redeposition agent which unexpectedly gives superior cleaning and prespotting capabilities to the detergent.
Moreover, it has been unexpectedly found that the hydrolyzed alpha olefin maleic anhydride copolymers useful in the present invention are in a range of C.sub.6 to about C.sub.24 and specific polymers containing at least two different alpha olefins of C.sub.2 to C.sub.30+ carbon content, and most preferably, C.sub.6 to C.sub.10 copolymers, are able to bring together as a coupling agent the nonionic surfactants and the builders in such a manner as to present a clear, stable, single-phase liquid detergent composition which has the aforementioned prespotting and increased detergency. The prior art fails to teach the method of using the specific hydrolyzed maleic anhydride polymers of the present invention as hydrotropes to produce such clear and stable nonionic surfactant-containing built liquid detergent compositions.
Rosnati, U.S. Pat. No. 3,208,949 discloses ethylene maleic anhydrides and polyvinyl methacrylate maleic anhydride interpolymers for use in a heavy duty or built liquid detergent system. The Rosnati patent discloses the use of a caprylic acid salt to function as a binary system to stabilize a built detergent into a substantially homogeneous pourable liquid detergent. The present invention does not contemplate the use of caprylic acid salts or any other type of binary agent for stability of the phases. Rather, the hydrolyzed alpha olefin maleic anhydride polymers by themselves are the stabilizing cleaning agents with the anti-redeposition properties for which Rosnati uses caprylic acid salts. Accordingly, the present invention differs from Rosnati.
Tsukuni et al., U.S. Pat. No. 3,830,745 depicts a detergent composition which includes anionic or nonionic surface active agents, and as a builder, a novel water soluble salt of a copolymer of cyclopentene or its derivatives with maleic anhydrides. These cyclopentene maleic anhydride copolymers are hydrolyzed to form an alkali metal carboxylate salt to function as novel builders. The molecular weight of the copolymer is stated as 350 to 2000. It must be understood that this is a powder system and does not encompass the liquid detergent system of the present invention. Tsukuni does not contemplate a clear, stable, single phase built liquid detergent in which an alpha olefin maleic anhydride copolymer of a carbon range of C.sub.6 to about C.sub.24 and polymers containing at least two different alpha olefins of C.sub.2 to C.sub.30+ and most preferably, C.sub.6 to C.sub.10 copolymers, functions as a hydrotrope to bring two normally incompatible phases of a liquid detergent together into a clear homogeneous solution. Moreover, since only cyclopentene maleic anhydride copolymers are utilized, it is obvious that the hydrotropic anti-redeposition properties inherent in the hydrolyzed alpha olefin maleic anhydride polymer of the present invention would not be apparent because the families of cyclopentene maleic anhydride copolymers and the alpha olefin maleic anhydride polymers of the present invention are different. Accordingly, the present invention differs from and is an improvement over Tsukuni et al.
Cooney, U.S. Pat. No. 3,852,213 discloses chelating compositions comprising 90 to 70% of polyvinyl methacrylate maleic anhydride copolymer and 3 to 30% borax, detergent dyeing, scouring and similar compositions containing the ingredients and a process for chelating varies Group II and Group III metal ions. The polyvinyl methacrylate maleic anhydride copolymer does not contemplate the hydrolyzed alpha olefin maleic anhydride polymers useful in the present invention. Accordingly, the present invention differs from Cooney.
Grifo et al., U.S. Pat. No. 3,328,309 depicts a liquid detergent composition having a surface active detergent ingredient in a liquid medium. The detergent may be any commonly used surfactants of the nonionic and anionic types and mixtures thereof. The Grifo et al. disclosure is important from the aspect that polymeric anhydrides having ethoxylated esters and anhydrides are similar but not the same as the hydrolyzed alpha olefin maleic anhydrides useful in the present invention. Indeed, the closest example between the alpha olefins of the present invention and those of the Grifo disclosure are propylene maleic anhydride copolymers.
The copolymers of Grifo et al. are all partial esters made by heating the anhydrides with ethoxylated or hydroxy containing surfactants to make partial esters. The present invention does not utilize such anhydride compositions and so differs from Grifo et al.
Renold, U.S. Pat. No. 3,509,059 depicts a stable, heavy duty liquid detergent composition which contains high electrolyte content as a builder which is produced in a stabilized form by polymerizing to a polymer a monomer in the presence of the detergent material. The polymer acts as a stabilizer for the compositions. The Renold composition differs from the present invention in that Renold is essentially a polymerization of an alpha, beta-unsaturated carboxylic acid to a surfactant. In other words, this is a polymer which is grafted onto a surfactant. The acid has to be converted to salt first in order to have a functioning system. Thus, it can be seen that this is not a polymer such as is used in the present invention but a grafted polymer. It follows that the stabilizing agent of Renold is chemically very different from the hydrotrope or stabilizing agent of the present invention. Accordingly, the present invention differs from Renold.
Tuvell, U.S. Pat. No. 3,235,505 teaches a liquid detergent emulsion with excellent stability against phase separation even though they are built detergent compositions. The excellent emulsion stability is said to be due to the presence of maleic anhydride type polymers wherein the comonomer is an olefinically unsaturated compound having less than 5 carbon atoms such as ethylene, propylene, isobutylene, vinyl methyl ether and the like. The maleic anhydride polymers used in the Tuvell emulsions can further be cross-linked with a diamine or a diolefinic compound. The Tuvell compositions differ from the present invention in that emulsions rather than solvated compositions are to be made. Tuvell also describes the final liquid detergent product obtained by his process as being very fluid and very white in color (see Example I) while the compositions of the present invention are required to be clear which are not taught in the Tuvell Patent.
Smith et al., U.S. Pat. No. 4,525,291 teaches built liquid detergent compositions which are single phase, clear and contain hydrogen peroxide along with stabilizers for that ingredient. However, it does not suggest the use of hydrolyzed polymers of maleic anhydride with certain alpha olefins as hydrotropes in such compositions.